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Heterogeneity of Induced Testicular Interstitial Cell Tumors of Mice as Evidenced by Steroid Biosynthetic Enzyme Activities¹

American Medical Center at Denver, Spivak, Colorado 80214

Quantitative enzyme studies (17-hydroxylase, 17,20-desmolase, 21-hydroxylase, and 20-hydroxydehydrogenase), using as a source of enzyme small fragments (25–48 mg) of estrogen-induced testicular interstitial cell (Leydig cell) tumors of mice and their first generation transplants in castrate male isogeneic hosts, show rather conclusively that such tumors are composed of heterogeneous populations of hormone-producing cells. Our data supported the original concept that, during tumor induction or shortly thereafter, several enzyme systems involved in steroid biosynthesis in Leydig cells decrease in an apparently random fashion. However, it appeared evident that at least in certain neoplastic interstitial cells the activity of 20-hydroxydehydrogenase, an enzyme whose functional significance has not yet been clearly established, increased significantly.

¹ This investigation was supported by USPHS Research Grants CA-05191 and CA-06841 from the National Cancer Institute, NIH.

² Present address: Departamento de Investigacion y Enseñanza, Centro Medico Nacional, Instituto Mexicano del Seguro Social, Mexico City, D. F., Mexico.

Received 6/ 5/67. Accepted 10/20/67.